This invention relates to a method for plating electrochemically aluminum efficiently by use of a composition containing aluminum.
Electroplating of aluminum can be done with difficulty in a plating bath of an aqueous solution system, because affinity of aluminum for oxygen is great, with the potential being baser than hydrogen. For this reason, electroplating of aluminum has been investigated in non-aqueous solution systems, particularly in a plating bath of an organic solvent system.
As such organic solvent system plating bath, a solution of aluminum chloride and LiAlH.sub.4 or LiH dissolved in ether or a solution of aluminum chloride and LiAlH.sub.4 dissolved in tetrahydrofuran is a representative example (e.g. D. E. Couch et al, J. Electrochem., Vol. 99 (6), p. 234). However, since all of these plating baths contain very active LiAlH.sub.4 or LiH therein, if oxygen or moisture exists, the reaction with those occurred to effect decomposition, whereby current efficiency was lowered, or the life of the bath became shortened. Also, the boiling point of an organic solvent is low, thus having a problem that the risk of explosion or combustion is high.
Further, as another example, there has been also proposed a plating bath of triethyl aluminum and NaF dissolved in toluene (R. Suchentrunk, Z. Werkstofftech, vol. 12, p. 190). However, also in this case, handling of triethyl aluminum with high danger poses a very great problem, and practical application thereof may be considered to be difficult.
As described above, although the prior arts may be somewhat successful in the technical task of plating aluminum, they can be hardly said to be widely applicable in general as practical technique because of difficulty in handling of the chemical substances employed.